This invention relates to a liquid level controller. The invention is particularly adapted to be used in a environment where the liquid level is proportional to air flow through a restricted opening, wherein the liquid level determines the degree of restriction. Such an environment is, for example, a waterpan-type spray booth of the type wherein air propelled by a ventilation fan entrains extraneous spray, for example, paint or other types of finishes, from the proximity of the waterpan through a restricted opening. Environmental and health regulations now require toxic and hazardous substances to be removed from air, especially in the vicinity of workers.
The restricted opening of the spray booth is defined by the water level and the bottom edge of a washing enclosure. The air flows through the restricted opening into a washing zone where the extraneous spray is washed from the air into the waterpan. Air is pulled into the washing enclosure by a ventilation fan which creates a negative air pressure flow through the restricted opening.
In order to properly entrain the extraneous spray in the air flow, it is necessary to maintain a proper velocity of air flow through the restricted opening. Since the bottom edge of the washing enclosure is stationary, a drop in water level in the pan as a result of evaporation or any other cause increases the size of the opening and correspondingly decreases the air velocity. Of course, the pan may be observed and filled manually when desired. However, the invention according to this application permits careful, automatic control from a remote location.